1. Field of the Invention
The present invention relates to a hydraulic braking system for use in an automotive vehicle, and more particularly to a hydraulic braking system which comprises a hydraulic braking pressure generator having a power chamber communicated with a power source, a plurality of wheel brake cylinders connected to the hydraulic braking pressure generator and to a reservoir, and valve means for controlling the communication between the hydraulic pressure generator and the wheel brake cylinders and the communication between the reservoir and the wheel brake cylinders.
2. Description of the Prior Art
The apparatus with the valve means described above is known as so called anti-skid apparatus which prevents the road wheels from locking in braking operation.
In accelerating operation, it is necessary to prevent a slip on driven wheels of the road wheels, for providing an optimum accelerating performance. For this purpose, a connecting valve is disposed in a hydraulic passage connecting the hydraulic braking pressure generator to the wheel brake cylinders provided on the driven wheels, at a position upstream of the above-described valve means disposed in the hydraulic passage, as disclosed in U.S. Pat. No. 4,565,411.
According to the hydraulic brake system described above, the road wheels are prevented from locking in braking operation by suitably controlling the hydraulic braking pressure applied to the wheel brake cylinders by means of the valve means, and the slip of the driven wheels is prevented in starting or accelerating operation by means of the valve means and the connecting valve which normally interrupts the flow between the wheel cylinders of the driven wheels and a pressure accumulator, i.e. the power source. In the above-described hydraulic brake system, a single connecting valve may be disposed in a passage connecting the hydraulic braking pressure generator to the wheel brake cylinders of the driven wheels.
However, in the case where a diagonal dual circuit is employed, in which a first passage connects the hydraulic braking pressure generator to one of the wheel brake cylinders of the driven wheels and one of the wheel brake cylinders of the free wheels, and a second passage connects the same to the rest of the wheel brake cylinders, the connecting valve must be disposed in each of the first and second passages, as in the case where all the road wheels are the driven wheels. In these cases, therefore, at least two sets of the connecting valve are needed to be disposed and corresponding arrangement of passages is necessary, so that the braking system as a whole becomes costly, large and heavy.